1. Field of the Invention
The present invention relates to methods and devices for bacterial, fungal and/or viral sterilization and disinfection; and, is more particularly directed to an apparatus and method for reducing dosage time in ultraviolet germicidal irradiation.
2. Description of Related Art
Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms. One mechanism by which UV-C deactivates microorganisms is by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions. The administration of UV-C radiation is becoming widely adopted by many hospitals as a more effective and reliable means of surface disinfection, as compared to the use of chemical cleaning agents alone. The effectiveness of germicidal UV-C irradiation depends on factors such as the length of time a microorganism is exposed to UV-C, the intensity and wavelength of the UV-C radiation, the presence of particles that can protect the microorganisms from UV, and a microorganism's ability to withstand UV-C during its exposure. In air and surface disinfection applications, the UV effectiveness is estimated by calculating the UV dose to be delivered to the microbial population. A method of calculating UV dose is as follows: UV dose μWs/cm2=UV intensity μW/cm2×Exposure time (seconds).
Germicidal UV for disinfection is most typically generated by a mercury-vapor lamp. Low-pressure mercury vapor has a strong emission line at 254 nm, which is within the range of wavelengths that demonstrate strong disinfection effect. The optimal wavelengths for disinfection are close to 265 nm. UV-C LEDs use semiconductors to emit light between 255 nm-280 nm. The wavelength emission is tunable by adjusting the material of the semiconductor. Although the germicidal properties of ultraviolet (UV) light have long been known, it is only comparatively recently that the antimicrobial properties of visible violet-blue 405 nm light have been discovered and used for environmental disinfection and infection control applications. A large body of scientific evidence is now available that provides underpinning knowledge of the 405 nm light-induced photodynamic inactivation process involved in the destruction of a wide range of prokaryotic and eukaryotic microbial species, including resistant forms such as bacterial and fungal spores. Violet-blue light, particularly 405 nm light, has significant antimicrobial properties against a wide range of bacterial and fungal pathogens and, although germicidal efficacy is lower than UV light, this limitation is offset by its facility for safe, continuous use in occupied environments.